1. Field of the Invention
The present invention relates to a communication signal receiver and a related signal processing method, and more particularly, to a method and apparatus utilizing an infinite impulse response (IIR) to replace a feedback equalizer (FE), for decreasing the complexity of a backend decoder and improving the efficiency of the whole system.
2. Description of the Prior Art
A conventional communication signal receiver usually includes the following functional blocks: a matched filter, a timing recovery circuit, an equalizer, an interference canceller and a decoder. The above-mentioned functional blocks need to be operated with proper parameters. The signal receiver may utilize a data-aided method to find the proper parameters via known data transmitted from a corresponding transmitter. However, the IEEE 802.3 Standard does not adjust these functional blocks by transmitting known data. Therefore, the adjusting of the parameters needs to be utilized through a decision-directed method.
At present, a conventional equalizer commonly contains a liner feed-forward equalizer (LE) and a decision feedback equalizer (DFE), wherein the DFE usually includes a feed-forward filter and a feedback filter. The DFE can effectively cancel the post-cursor component of the signal, but it cannot sufficiently prevent the error propagation phenomenon, thereby the system performance is deeply affected.
If a Viterbi decoder is directly connected to an output of the DFE, the decoding capability of the Viterbi decoder will also be deeply affected by the error propagation. There are several published works about reducing the error propagation and the related solutions have been disclosed in U.S. Pat. No. 7,272,177 and U.S. Pat. No. 7,453,935, etc. Referring to U.S. Pat. No. 7,272,177, a decision feedback sequence estimator (DFSE) is utilized to detect the data transmitted from the DFE, but the parameters of the FE need to be provided to the DFSE. Additionally, a tentative decision is needed to provide the slicer error to adjust the afore-mentioned blocks. Therefore, a tentative decision composed by an FE and a slicer is implemented with a DFSE, for providing the parameters of the FE to the DFSE. In this prior art, the error propagation phenomenon can be decreased, but the complexity of the system will be increased by a significant degree, and the Viterbi decoder cannot derive a best decoding gain (i.e., a best solution of the Maximum likelihood sequence estimation (MLSE)). U.S. Pat. No. 7,453,935 only adopts one FE, which decreases the cost resulting from the implementation of an FE, but makes the backend processing become very complicated.